While flexible magnetic blend compositions have been known for some time, a high temperature, oil resistant, flexible high energy ferrite magnetic material in strip form has continued to be a target for research and development. In particular, there has been interest in finding such a material for automotive applications, including, for example, electromechanical applications in this area. Such a material would be of great interest for use in making permanent magnet motor stators and rotors.
In particular, it has been known to use a conventional nitrile rubber system containing chemical curing agents, such as sulfur. An example of such a product is sold by Minnesota Mining and Manufacturing Corp., (3M), St. Paul, Minn., under the designation B1030. It is believed that this product is made by laminating shear oriented calendered sheets under heat and pressure to build-up the final thickness. If the thickness of the laminated sheet as molded is not precise, it is ground to size, leaving a relatively dirty surface (i.e., the ferrite particles at the surface are loose). The final cured sheet cannot be reprocessed or recycled. Aging of the laminated sheet or strips cut from it at temperatures above 100.degree. C. is rapid and results in severe embrittlement. This is due in part to the chemical unsaturation of the backbone of the binder system, and in part to the residual curing agents which remain after the initial cure.